The Power of H1's

[jaudette3]

I'm continuously adding content to my website and was doing a little light (sorry) reading last night, a publication by Bosch titled "Bosch Automotive Electrics and Automotive Electronics". As a lighting geek, I thought some of the information on lighting was interesting. For example, I have to admit I have never given much thought to what "asymmetric" meant when describing an asymmetric lens, such as those used on the early Euro headlights, H1's and H4's. An asymmetric lens is a clever device using optics that distribute the light unevenly, in this case with low beams.

Here's a graphic of an asymmetric headlight's low beam light distribution:



and one of high beam light distribution:



As you can see, the low beam light is directed far down the road in your lane, but on the side of approaching traffic it has a much small pattern in order to keep the light out of the eyes of on-coming drivers. I surmise that that is what the prism (the same Fresnel lens technology used in lighthouses around the world) on the driver's side of the lens does. The high beam light covers things much more broadly.

This really reinforces my high opinion of H1's. The ability to adjust their low and high beams separately enables you to set the low beams conservatively while aggressively aiming the high beams far down the road. I'm sure these were born out of a need for adequate illumination for high speed Autobahn type driving. Not a good idea then - or now - to out-drive your headlights. I suspect that's one of the main reasons that lighting technology was moving forward in Europe while stagnating with DOT imposed sealed beams in the U.S. You don't need great lighting at 55MPH.

Cheers,
John

[jaudette3]

After reading the article I got out an H1 and tried to get an idea of how it manages the light. There is an interesting graphic in the article of how an H4 broadcasts light (couldn't find one for H1's, but I think they're somewhat comparable). Here it is:



Here's the legend:

#1 - Low beam filament
#2 - Shield
#3 - High beam filament

And a picture of a LHD H4 lens:



Now it's easy to see why the prism is on the side of the driver. As you can see, all of the light bounces off of the reflector (which is why you need the reflectors to be in great condition). The low beam projects off of the reflector at a downward angle. While the graphic and picture are of an H4, an H1 works pretty much the same. When you look at an H4 or H1 lens you can see what happens. The upper rays of the low beam are broadcast unimpeded while the lower rays are "bent" downward by the prism, keeping them out of approaching drivers eyes. The high beam projects off of the lower part of the reflector (of course the H1 has it's own, separate high beam reflector) and is broadcast outward, underneath and unimpeded by the prism.

[37yrold911]

Thx - very informative. You might want to check out any old info you can get on Cibie "Z-beams" - also a comparison ot LED, Litronic, etc. would be fun.

Then there are the biodes...

[sithot]

Informative. Thanks.

There is a good article on both HID and LED lighting in one of the UK P-Car rags. LED's don't require ballasts which is a plus. They are a little odd looking but functionality is very good.

[jaudette3]

A bit more information on my website: http://www.audettecollection.com/the-power-of-h1s/

Cheers,
John